German Patent Applications DE 23 30 109, DE 25 27 321, DE 26 19 547 and DE 26 33 905 and the U.S. Pat. No. 4,038,396 describe 2-(substituted phenyl)-oxazolo[4,5-b]pyridines, -oxazolo-[4,5-c]pyridines and -oxazolo[5,4-b]pyridines as antiinflammatory, antipyretic and analgesic compounds.
German Patent Application DE 23 61 757 describes 2-(substituted phenyl)-imidazo[4,5-b]pyridines having antihypertensive, positively inotropic, platelet aggregation-inhibiting and bleeding time-prolonging properties.
European Patent Application EP 022 495 describes 2-(substituted phenyl)-imidazo[4,5-b]pyridines as cardiotonic agents and hypertensive agents. European Patent Application EP 072 926 describes 2-(substituted phenyl)-imidazo[4,5-b]- and -[4,5-c]pyridines having positively inotropic properties. European Patent Application EP 079 083 describes 2-phenylimidazo[4,5-c]pyridines having vasodilating, positively inotropic and platelet aggregation-inhibiting properties, which have no inhibitory action on myocardial phosphodiesterase.
PCT Application WO94/12461 describes, inter alia, 2-(substituted phenyl)-imidazopyridines and -oxazolopyridines as selective inhibitors of phosphodiesterase of type 4.